Most sore throats come from viral infections, which account for roughly 90% of all cases. But viruses are far from the only cause. Bacteria, allergies, acid reflux, and even the air in your home can all irritate your throat and leave it raw and painful.
Viral Infections: The Most Common Cause
The same viruses that give you a cold or the flu are responsible for the vast majority of sore throats. Rhinoviruses (the common cold), influenza, and coronaviruses all inflame the lining of your throat as your immune system fights them off. These sore throats typically arrive alongside other symptoms like a runny nose, coughing, sneezing, or body aches, and they resolve on their own within a week or so.
Two viral infections deserve special mention. Cold sores caused by the herpes simplex virus can produce throat pain, especially during a first outbreak. And the Epstein-Barr virus, which causes mononucleosis (“mono”), brings on a particularly severe sore throat along with deep fatigue, fever, swollen lymph nodes in the neck, and sometimes an enlarged spleen. Mono is most common in teenagers and young adults. Most people recover in two to four weeks, though the fatigue can linger for months.
Strep Throat and Other Bacterial Infections
Group A Streptococcus is the bacterium behind strep throat, the most common bacterial cause of a sore throat. It accounts for 15 to 30 percent of sore throats in children and 5 to 15 percent in adults. Unlike viral sore throats, strep tends to come on suddenly and without the typical cold symptoms like coughing or a runny nose.
Strep throat usually develops two to five days after exposure. Common signs include fever, painful swallowing, red and swollen tonsils (sometimes with white patches or streaks of pus), swollen lymph nodes at the front of the neck, and tiny red spots on the roof of the mouth. Children may also experience headache, nausea, vomiting, stomach pain, or a rash known as scarlet fever.
One practical way doctors gauge the likelihood of strep is a scoring system that looks at five factors: your age, whether you have a fever above 100.4°F, swollen or pus-covered tonsils, tender lymph nodes in the front of your neck, and whether you have a cough. If most of those line up (and you don’t have a cough), the probability of strep can be over 50%. If only one or two apply, the chance drops to 10% or less. A rapid strep test or throat culture confirms the diagnosis.
Untreated strep can lead to complications if the bacteria spread. These include abscesses around the tonsils, ear and sinus infections, rheumatic fever (which can damage the heart, joints, and brain), and a kidney condition called post-streptococcal glomerulonephritis. This is why strep throat, unlike a viral sore throat, requires antibiotics.
Postnasal Drip and Allergies
Allergies are one of the most overlooked causes of a chronic or recurring sore throat. When your body reacts to pollen, dust mites, pet dander, or mold, your nasal passages produce excess mucus. That mucus drains down the back of your throat, a process called postnasal drip, and irritates the tissue along the way. Your tonsils and surrounding throat tissue can swell, leaving you with a persistent scratchy or sore feeling that no amount of cough drops seems to fix.
The key difference from an infection is timing. Allergy-related sore throats tend to follow seasonal patterns or flare up in specific environments. They also come with itchy eyes, sneezing, and nasal congestion rather than fever or body aches.
Silent Reflux
Acid reflux doesn’t always announce itself with heartburn. A condition called laryngopharyngeal reflux, often nicknamed “silent reflux,” sends small amounts of stomach acid and digestive enzymes up into the throat. Your throat lining is far more sensitive than your esophagus. It lacks the same protective coating and doesn’t have the mechanisms to wash acid away quickly, so even a small amount of reflux can cause ongoing irritation.
Silent reflux produces a distinct set of symptoms: chronic sore throat, hoarseness or a lower voice, a persistent feeling of something stuck in your throat, frequent throat clearing, excessive mucus, and a chronic cough. Many people with this condition never experience the classic burning sensation in their chest, which is why it often goes undiagnosed. The stomach acid also interferes with your throat’s ability to clear mucus and fight off infections, making you more susceptible to upper respiratory problems.
Dry Air and Environmental Irritants
Breathing dry air, especially during winter when indoor heating strips moisture from the air, can leave your throat scratchy and sore. Your throat relies on a thin layer of mucus to stay comfortable and protected. When humidity drops too low, that mucus coating dries out and your throat becomes inflamed. Keeping indoor humidity between 30% and 50% helps prevent this. Going above 50% creates its own problems, including mold growth and dust mite proliferation.
Other environmental factors that irritate the throat include cigarette smoke, air pollution, chemical fumes, and prolonged mouth breathing (common when you’re congested or during sleep). Yelling, singing, or talking loudly for extended periods can also strain the muscles and tissues in your throat, producing soreness that mimics an infection but stems from overuse.
When a Sore Throat Signals Something Serious
Rarely, what feels like a sore throat can indicate a more dangerous condition. Epiglottitis is an inflammation of the small flap of tissue that covers your windpipe during swallowing. When it swells, it can partially or completely block your airway. Warning signs include a high-pitched whistling sound when breathing in (called stridor), difficulty swallowing, drooling, and needing to sit up or lean forward to breathe. In children, these symptoms can progress rapidly. Epiglottitis is a medical emergency that requires immediate treatment.
A peritonsillar abscess, which is a pocket of pus forming near the tonsils, can also cause severe throat pain that’s noticeably worse on one side, along with difficulty opening the mouth, muffled voice, and fever. This typically develops as a complication of untreated strep throat or tonsillitis and needs medical drainage.